We've been able to toggle visibility of gists since 2014 (https://github.com/blog/1837-change-the-visibility-of-your-gists), but I just noticed that I can no longer make public gists private. That is, when I edit private gists I still see the "Make Public" button, but not the other way round — there's only a "Delete" button when I edit public gists; the "Make Secret" which should be next to it (as shown in the screencast in the linked blog post) is nowhere to be found. I made a screenshot and a screencast demonstrating the issue, both of which are attached. Could you please confirm this issue? Was this an intentional change, and why? Thank you for your attention.https://cloud.githubusercontent.com/assets/4149852/16898407/c76db210-4c0b-11e6-9108-0450f1edebb4.gif)
Thanks for writing in!
We had to remove that functionality because it was misleading. Turning a public gist into a secret one doesn't change the URL, which means anybody with the old public URL can still access it.
We may consider improving this in the future, but for now, you will have to delete the public gist, and create a new secret one with the same content.
Creating a new secret gist gives it a new unique URL. You can share that URL with just the people you want to be able to see the gist.
Please let me know if you have any other issues!